1. Field of the Invention
This invention relates to novel derivatives of phthalazine and, more particularly, to 1-(3- or 4-substituted piperidino)phthalazines useful as cardiac stimulants and as phosphodiesterase inhibitors.
2. Description of the Prior Art
Quinazolines, reported to be cardiac stimulants, are claimed in U.S. Pat. No. 4,001,422.
German Offenlegungsschrift No. 2021195 discloses as anti-inflammatory, particularly antirheumatic agents, and as immunosuppressants, a series of 1-(substituted amino)- or 1-heterocyclicphthalazine derivatives. None of the compounds are reported to be cardiac stimulants.
British Pat. No. 1,133,406 describes a group of 1-(substituted amino)-4-(hydroxy- or alkoxyamino)-phthalazines and 1-heterocyclyl-4-(hydroxy- or alkoxyamino)phthalazines which are useful as antipyretic, antiinflammatory, hypotensive, bronchodilator and respiratory stimulant agents.
British Pat. No. 1,303,061 discloses as antiinflammatory agents, and in some cases as immunosuppressants, 1-aryl-1-aralkyl-4-aminophthalazines.
British Pat. No. 1,199,768 discloses a limited number of 4-aminoquinazoline derivatives as antihypertensive agents.
Copending application Ser. No. 908,664, filed May 23, 1978 and now abandoned, describes related 6,7-dimethoxy-1-(4-substituted piperidino)phthalazines useful as cardiac stimulants. Said compounds have the formula I wherein R is methyl and Y is a 4-position substituent and is defined as --X--(CHR.sup.1).sub.m -Z wherein X is a direct link, m is 0 and Z is as defined above, with the exception that Z never contains a cycloalkyl group.